MRI machines have some pretty powerful magnets, but they still won't accelerate anything to the speed of sound, let alone an object held reasonably securely and only within the space of ~12 inches.

It's not a particularly large or sharp object; I could see it being pulled through the inside of a chest cavity mostly pushing stuff out of the way. Definitely 'major injuries' though.

[–] Donkter 12 points 10 months ago

I would guess speed of sound is the upper limit of what MRIs can accelerate small metal objects to. So it's easy shorthand for an author who didn't know anything about MRIs before writing the article to reference. obviously something so large and inside a human would not accelerate to those speeds.